November
Chemistry World Podcast - November 2011
01:22- World's longest carbon-carbon bond created
04:20- Pitcher plant inspires ultimate non-stick surface
07:54- NASA's John Grotzinger discusses the difficulties of getting the Curiosity rover to Mars with its massive payload of analytical instruments, and what it will do when it gets there
15:55- Conjuring up gram quantities of a stabilising anion
19:07- Bacteria: the ultimate secret agent
22:38- Ever felt you're facing the world alone? This year's chemistry Nobel laureate Dany Shechtman fought hard to establish the idea of quasicrystals in the face of criticism. Hans-Rainer Trebin from the University of Stuttgart explains a little about the story and what a quasicrystal is
29:37- Chameleon clothes to detect falling oxygen levels
32:23- Patching up patients with a heart of gold
36:14- Trivia - Why is 23 October an important day for chemists?
(Promo)
Brought to you by the Royal Society of Chemistry, this is the Chemistry World Podcast.
(End Promo)
Interviewer - Chris Smith
This month, we're off to Mars in a mini, well almost.
Interviewee - John Grotzinger
The thrusters will push against the gravitational pull of Mars until it hovers, maybe 20 meters or so above the surface and then it reels the rover out on a set of cables down to the surface of the planet.
Interviewer -- Chris Smith
That's NASA's John Grotzinger, the chief scientist behind the curiosity Mars rover machine, which blasts off to the red planet later this month. We'll hear from him how you get a car-sized rover down in one piece and the chemistry it's destined to do later in the program. Hello I'm Chris Smith. Welcome to the November 2011 edition of the Chemistry World podcast. Also with me this month are Phillip Broadwith, Laura Howes and Patrick Walter and they'll be talking about the creation of the world's longest chemical bond and the world's slipperiest substance. Plus it's your chance to brush up on what a quasicrystal is when we take a look at this year's Nobel Prize for chemistry.
(Promo)
The Chemistry World Podcast is brought to you by the Royal Society of Chemistry. Look us up online at chemistryworld dot org.
(End Promo)
(01:22 - World's longest carbon-carbon bond created)
Interviewer - Chris Smith
And to kick us off in the world of chemical bonds, size and certainly length are definitely important. Phil.
Interviewee - Phillip Broadwith
Absolutely Chris and one of the things that lot of chemists are trying to do is to trying to make the longest bonds they possibly can to test out the limits of, you know, how strongly atoms are held together and how they can design molecules that have particular shapes or particularly strained and weak bonds that might be particularly reactive in different ways or things like that.
Interviewer - Chris Smith
Indeed. So what have they done here?
Interviewee - Phillip Broadwith
This group led by Peter Schreiner at the Justus Liebig University in Germany has made what they're claiming as the longest carbon-carbon bond in an alkane. It's 1.7 angstroms long, which is a little bit longer than a normal, sort of a carbon-carbon bond, averaged at about 1.5 angstroms. So, it's a little bit longer.
Interviewer - Chris Smith
So, how they actually done this because my understanding is that when you actually bond something together covalently like a hydrocarbon, it's because the clouds of electrons from one atom interact with the clouds of electrons from the second atom and you bring about a bond. So, how can you manipulate the length of that?
Interviewee - Phillip Broadwith
Okay Chris, well that interaction is the same but that's if you're just talking about those two atoms. What chemists generally do to try and elongate these bonds is to attach other stuff to those atoms of the covalent bond. So, if you attach great big, bulky groups to those two atoms, you get like a dumb-bell shaped molecule. So the carbon-carbon bond is the bar of the dumb-bell and you've got this other bulky stuff attached to the carbons on either end.
Interviewer - Chris Smith
And those two big bulky things repel each other and that pushes the bond apart.
Interviewee - Phillip Broadwith
Yeah. So, the bulky stuff on either end literally just pushes the bond apart and puts strain on that bonding interaction, which just holds the carbon atoms just a little bit further apart, far enough apart that they can still just about interact and make a bond, but that bond is much weaker.
Interviewer -- Chris Smith
Now you mention that there could be some use in understanding this kind of thing because you know that you could use this sort of chemistry to create bits of molecules that are bit more vulnerable to that bond breaking than in another region or something. Are there any ways where this could immediately be exploited or applied then?
Interviewee - Phillip Broadwith
Probably not directly, but the interesting thing about this particular work is that basically to make these kind of long bonds stable, you need not just a repulsion but some kind of attractive force to balance that out just enough to keep the bond together and what Schreiner and his group have done is use a van der waals interaction. So the big bulky molecules that they've got on either end of their carbon-carbon bond have relatively flat faces that are covered in hydrogen, and they have just enough van der waals atraction between them to keep the bond together. And so using that principal, you could think about designing other molecules, or using it to stabilize different kinds of new molecules and materials.
(04:20 - Pitcher plant inspires ultimate non-stick surface)
Interviewer -- Chris Smith
Thank you Phil, new flies on him. Talking of flies, tell us about this pitcher plant inspired slippery stuff, Patrick, apparently the most slippery substance known to man apart from Tony Blair has been invented.
Interviewee - Patrick Walter
(laughs)Okay. So Joanna Aizenberg's group at Harvard University were looking at new ways to develop omniphobic material. So these are materials that repel both liquids like water, and also organic liquids like oil.
Interviewer - Chris Smith
Have we not already got super-slippery substances and what's Teflon then?
Interviewee - Patrick Walter
Yeah, Teflon is a super-slippery substance, but it's kind of different to the other kind of nano-engineered approaches they've been looking at. So people have been looking at super-hydrophobic slippery surfaces based on the lotus leaf. So the lotus effect is based on miniature papillae that sit on top of the lotus leaf and when something like water rests on the lotus leaf, the small pockets of air trapped beneath the water droplets, this creates nice round droplets to just roll straight off. But this doesn't work for oils because oils do not have the surface tension that water does. So they just collapse. So they wet the leaf.
Interviewer -- Chris Smith
So they're just going to get underneath the air.
Interviewee - Patrick Walter
Exactly.
Interviewer - Chris Smith
And displace the air around.
Interviewee - Patrick Walter
So, what Joanna Aizenberg has done is she's tried to copy the pitcher plant. So pitcher plants are plants that grow throughout Southeast Asia. These plants have a bulb which is filled with a digestive fluid and when insects land on the top of this opening of this bulb, they just simply slip off and fall in. So they started looking into why this happens and they wanted to copy it.
Interviewer -- Chris Smith
Why does it?
Interviewee - Patrick Walter
So, what's special about the pitcher plant is around the top of this bulb, where the insects tend to meet their rather unpleasant end, is there's this small, nano-sized pillars kind of sticking out from the plant's surface and this is coated in a kind of nectar. So this means that when the flies land on it, the oils don't grip, they just slip straight off in.
Interviewer -- Chris Smith
Oh! Because the fly's foot is oily, you got this watery layer on the surface of the plant. Oil and water when mixed, so you got fluid on fluid and it's slippery
Interviewee - Patrick Walter
So oil and water are immiscible, they're not going to mix and this creates a slipperiness.
Interviewer - Chris Smith
Now obviously they're not going to reinvent the oil making another pitcher plant. So what did this Harvard group do?
Interviewee - Patrick Walter
They had two different approaches. One approach was to create small nano-pillars a bit like many of these super-hydrophobic materials that have gone in the past and then a completely unstructured Teflon surface made with just a complete mixture of Teflon fibres and then what they did, copying the pitcher plant with its nectar liquid. They used a fluorinated compound. So, they just soaked this structure with it and this created a slippery surface. So, things like oils can't interact with this fluorinated compound and neither can water, it's immiscible with both. So anything that lands on it, they tested things like jam, ants.
Interviewer -- Chris Smith
It's a liquid, it's not a gas. With the lotus leaf, you've got air, this gas is compressible and displaceable, whereas if you have a liquid there, it won't get compressed, will it so?
Interviewee - Patrick Walter
Exactly. So what's very important is.
Interviewer - Chris Smith
It will work under very interesting condition
Interviewee - Patrick Walter
Yeah. This is very useful because it can work under high pressures, things like oil pipelines perhaps. It's self-healing, so it just keeps recovering if it gets knocked.
Interviewer -- Chris Smith
Something I think we wish we could all do. Thank you Patrick.
(07:54 - NASA's John Grotzinger discusses the difficulties of getting the Curiosity rover to Mars with its massive payload of analytical instruments, and what it will do when it gets there)
Interviewer - Chris Smith
Mars is the focus of the space science fraternities' attention this month, when Curiosity, a new rover machine blasts off on November the 25th. NASA's John Grotzinger is the chief scientist on the project.
Interviewee - John Grotzinger
The Curiosity rover differs from that of previous machines. In that it has a very involved set of instruments that are most complex that's ever been flown to the surface of another planet and between those instruments we should be able to make a variety of measurements and integrate the measurements that are made to create a new insight into the habitability of ancient environments on Mars as well as get a sense for the current surface environments of Mars.
Interviewer -- Chris Smith
First of all, how big is Curiosity?
Interviewee - John Grotzinger
Curiosity weighs 899.2 kilograms. It's about the size of a Mini Cooper.
Interviewer - Chris Smith
Wow! That's pretty big, is that not what an order of magnitude, larger than the ones that are down there at the moment?
Interviewee - John Grotzinger
It's about half an order magnitude. Spirit and Opportunity each weighed about 180 kilograms and with Curiosity weighing at 900, it's a very significant increase in the mass of the rover.
Interviewer - Chris Smith
And size too, so what are you going to pack into this Mini Cooper sized frame? What will go in there and why are we scaling up to this ginormous size?
Interviewee - John Grotzinger
The reason for the increase in the size is because we have two instruments that function within the internal environment of the rover, so they're sort of in the belly of the beast, if you will, and when we collect samples, we do it by drilling and we need a kind of a drill that's able to penetrate into rocks up to depths of about 5 centimetres, drill bits about a centimetre and a half a diameter and then it feeds these powders through a very complex labyrinth of processing elements, so that it comes out, the sample is sieved down to about a 150 microns and then it goes inside the rover and in there, we have these two very specialized instruments. So that's what results really in the increase of the mass.
Interviewer - Chris Smith
What sorts of rocks are you going to be drilling into? What are you looking for?
Interviewee - John Grotzinger
Well, we've chosen a landing site that sits quite near the equator of Mars, but near a feature called the dichotomy boundary, where Mars basically gets cleft into two different hemispheres of different topographic elevation and at that break in elevation, there's a spot called Gale Crater which is a topographic depression that's a 150 kilometres in diameter and within that depression is a great mound of layered strata and what we can see on the strata is evidence for what was formerly aqueous environments and we should be able to study effectively a series of time records within their earliest history of Mars and begin to understand its evolution from a very wet planet and possibly habitable to microorganisms to the dry planet that it is today.
Interviewer - Chris Smith
So this has got a small drill though, so you can only really metaphorically speaking, scratch the surface of the planet. So how far back in time do you think you'll be able to go?
Interviewee - John Grotzinger
Well, we know that the crater that contains this thick pile of strata is probably over 4 billion years old and then using some other evidence that we have available we suspect that the strata themselves are probably not much younger than 3 billion years. So somewhere between 4 billion and 3 billion years ago, we've got 5 kilometres of sediment that has been piled up to form these layers. To look at and that really represents the principal target debris after.
Interviewer - Chris Smith
What sorts of questions will you be able to answer? How Mars started off, how it evolved, got wet, got dry, and then possibly life?
Interviewee - John Grotzinger
What we're able to do is take advantage of the fact that these strata have been quite deeply eroded and so what was once buried is now exposed, we're able to tap right into what would originally have been the sort of the internal part of this mountain of strata and when you go from the lower to the upper layers, you're basically going from the oldest records of time to the youngest records of time and where there are sediments there are records of the environment and so by drilling and sampling our way up through this pile of strata, we're effectively given the chance to reconstruct not just the state of the environment early on in Mars, but also the way it might have evolved.
Interviewer - Chris Smith
But looking at the practicality from in it, how do you get almost a ton of rover out there? How long is it going to take to get there and then how do you get it down onto the surface of Mars once you arrive?
Interviewee - John Grotzinger
To begin with, we launch and then on the cruise from Earth to Mars, everything is pretty much the same, there is a solar array which keeps the rover charged; takes about eight months and then we begin to feel the pull of the gravitational field as we enter the planet's atmosphere and begin to descend, but this time, in contrast to previous Mars landed missions, the aeroshell which is the bit that you see in these videos, that sort of screaming along with flame shooting out beneath it, it's actually able to steer a little bit because we have an ejectable mass, and it offsets the centre of mass from the centre of symmetry and it allows it to fly a bit like an airplane wing and then there are thrusters that are activated to allow it to correct the trajectory and so instead of, sort of, plunging vertically through the atmosphere, it's actually coming down at quite a low angle and then when it decelerates to about Mach 2, it deploys a parachute, and that slows it down even further and then when we get down to may be a kilometre above the surface, the heat shield falls away and from that now, everything gets very different from previous missions. We now have a forced spacecraft called the power descent vehicle. And the power descent vehicle has eight rocket thrusters and beneath it is attached the rover pretty much ready to go with the wheels hanging down. The descent stage then will drop down the thrusters, while pushing against the gravitational pull of Mars until it hovers may be 20 meters or so above the surface and then it reels the rover out on a set of cables down to the surface of the planet and then there, the descent vehicle detects the change in mass because now the planet is partially supporting the weight of the rover. The cables are cut and the descent stage goes off and crash lands and the rover, unlike previous rovers, this one requires very little effort to actually get going. It's pretty much it lands ready to go, as a result of that process.
Interviewer - Chris Smith
And assuming it does go according to plan how long will Curiosity be able to drive around on the surface of the planet?
Interviewee - John Grotzinger
It's one Mars year, which is a bit longer than two Earth years, but if you compare it to MER, those were built to go three months, so with two years, who knows how long we'll be able to go?
Interviewer - Chris Smith
NASA's John Grotzinger and if you'd like to find out a bit more about Curiosity there is a terrific feature in this month's edition of Chemistry World magazine, which is well worth a read.
(15:55 - Conjuring up gram quantities of a stabilising anion)
Interviewer - Chris Smith
You're listening to Chemistry World with me Chris Smith. Still to come, sending messages by bacteria, and clothes that change colour according to how much oxygen there is around, but first we were talking about Teflon earlier, now we're back for more and this time to hear how you can stick it to boron, Laura.
Interviewee -- Laura Howes
A group led by Helge Willner from the Bergische University in Wuppertal were looking at trying to make large weakly coordinating anions. So these are very large spherical, symmetrical anions that their charge is ready to spread out, it's not really polarized, so it doesn't interact very much, but it can help stabilize these cations that are quite weak. One of the anions that people have been thinking about for a long time is boron, surrounded by Teflon group, so CF3.
Interviewer -- Chris Smith
Why would that be good?
Interviewee -- Laura Howes
Well, it would have all the properties that you'd want. I mean, the CF3 would mean that around it, it's not very polarized but because it's so large and like big, big ball. So it's sort of, you know, you've got your boron in the middle surrounded by these huge great big molecules and there's not really anywhere for the electrons to sort of go.
Interviewer - Chris Smith
I sense a but coming?
Interviewee -- Laura Howes
But, yes, they just couldn't make it. They tried various different ways of doing it, but they often found that it just wasn't going to work because of boron's lowest acid capabilities, they couldn't. Usually when you make an anion like this, you do look in substitutions. You put something on it; you take something off and put a different bit on it.
Interviewer - Chris Smith
Very laborious, very inefficient, so.
Interviewee -- Laura Howes
But boron, it just wasn't working
Interviewer - Chris Smith
So what have they done instead?
Interviewee -- Laura Howes
Instead, they've used these great interhalogen compound especially chloride trifluoride, so ClF3, which it will set fire if it interacts with just about anything. If you mix it with sand, it will set fire, if you mix it with asbestos, it will set fire, if you mix it with yourself, it will set fire. So there's not a lot of labs in the world that want to do anything with this stuff.
Interviewer -- Chris Smith
I'm not surprised. So what did they do with it?
Interviewee -- Laura Howes
You have to keep it under very cold conditions, keep it under a very inert atmosphere and just be very, very, very careful with it.
Interviewer -- Chris Smith
What do you keep it in?
Interviewee -- Laura Howes
I think, they keep it in stainless steel, but I wouldn't like to say for certain, it's been a while.
Interviewer - Chris Smith
Or try even.
Interviewee -- Laura Howes
No. (laughs)
Interviewer - Chris Smith
So they've managed to make this material safely.
Interviewee -- Laura Howes
They have managed to make it. They have now got up to sort of 62 grams of the stuff they got.
Interviewer - Chris Smith
So you have boron, you react it with this chlorine trifluoride.
Interviewee -- Laura Howes
So, actually what you work on is a boron with cyanide groups around it, and instead of substituting onto the boron, what you do instead is you add the fluorine to the carbon and break the C-N bonds of your cyanide and replace those with fluorines.
Interviewer -- Chris Smith
What could they do with it?
Interviewee -- Laura Howes
Well, at the moment, they've got to see whether it's actually got all the properties that they hope it has. At the moment, it's all just you know, it's a theoretical target they've got at and this is amazing. They think it's going to be pretty good. What they'd like to use it for ionic liquids, but obviously you need to have a good pairing and so this can help with that.
Interviewer -- Chris Smith
Why are ionic liquids important and what can we do with them?
Interviewee -- Laura Howes
Basically they're made by, you know, two ions, cation and an anion. There are ways of doing chemistry often without other solvents, so it can make thing without all the nasty sort of organic solvents often we try and avoid.
(19:07 - Bacteria: the ultimate secret agent)
Interviewer - Chris Smith
Well, from the nastiest chemical known to man to perhaps becoming one of the most useful onto something else, potentially nefarious but also with good intentions to bacteria that could send secret messages.
Interviewee - Phillip Broadwith
Well yes Chris. Next time, you get a spam message, maybe you should read it, at least that's if it's the kind of spam that David Walt at Tufts University of Massachusetts is talking about?
Interviewer -- Chris Smith
What Viagra offers mortgages and chair of a dead dictator in Nigeria's fortune?
Interviewee - Phillip Broadwith
Not quite Chris. It's a steganography by printed arrays of microbes. Steganography being the encoding of secret messages.
Interviewer - Chris Smith
Or spam for short, hence the acronym, okay. So what have they actually done?
Interviewee - Phillip Broadwith
The idea is that you take engineered strains of E. coli that are made to be fluorescent. They have taken seven different strains, which fluoresce in seven different colours and if you combine two of those together to make a sort of bit of information that gives you 49 different combinations, which is plenty to do all of the letters of the alphabet and numbers, bit of punctuation in bits and bulbs. You can then kind of put strings of those past together to make a message. So if for example, you put an orange strain with the green one, that's an 'i' and a yellow one with the red one that's an 'r' and what this team did was put enough of those together to spell out the message. This is a bio-encoded message from the Walt Lab @ Tufts University, 2011.
Interviewer -- Chris Smith
How do you read it?
Interviewee - Phillip Broadwith
Well the idea of transmitting the message is that the person you want to send the message grows up the bacteria in a little multi-well plate or something like that. You can then get a sheet of paper or nitrocellulose or something like that, press it onto the surface which transfers some of the bacteria, shift that in the post, the other person at the other end gets the sheet of cellulose, puts that into some growth medium, grows up the colonies of bacteria, and they start fluorescing and you can then read out the pairs of colours and get your message.
Interviewer -- Chris Smith
So what's the security side to this though?
Interviewee - Phillip Broadwith
Okay, well first of all you need to know that there's a message on the paper, it's pretty much invisible until you start growing the bacteria, but if you know that then you can add a second layer of cipher by using antibiotics. So, instead of in each well of just having one form of bacteria, you can have two different strains that different colours and are resistant to different antibiotics. So you then need to treat the whole thing with the right antibiotic to get the message and the group did that and so they encoded a message that if you treat it with Ampicillin, you get the same message that I said before about being a bioencoded message from the Walt Lab @ Tufts, but if you use kanamycin, which is a different antibiotic, you get the message that says you have used the wrong cipher and this message is gibberish and if you use a non-selective antibiotic, then you just get a complete load of guff anyway.
Interviewer -- Chris Smith
What do they say it could be used for though?
Interviewee -- PhillipBroadwith
Well, for the first then you got to rely on some kind of postal service which introduces a bit of a weak link especially if you're talking about a royal mail. It's kind of an experiment in a concept of sending messages, but there are ways that you can improve it even further. David Walt's talking about having bacteria that change the way they fluoresce over time, so you have a message that would automatically self-destruct. So, if your message is not particularly urgent, but you really need it to be secure, perhaps that's a possible application.
(22:38 - Ever felt you're facing the world alone? This year's chemistry Nobel laureate Dany Shechtman fought hard to establish the idea of quasicrystals in the face of criticism. Hans-Rainer Trebin from the University of Stuttgart explains a little about the story and what a quasicrystal is)
Interviewer -- Chris Smith
Puts a whole new spin on the idea of a message going viral. Thank you Phil. Last month was Nobel time again and the chemistry prize this year went to the Israeli scientist, Dany Shechtman for his discovery of the concept of quasicrystals. But it was no plain sailing for Shechtman beforehand. He endured a very rough ride, when he first announced his findings in the 1980s including a scathing put down from the chemist, Linus Pauling. He described the work as nonsense remarking there is no such thing as quasicrystals, only quasi scientists. Well that got proved wrong, but if like me, you only have a quasi understanding of what a quasicrystal is then may be physicist Hans-Rainer Trebin from Stuttgart University can help
Interviewee -- Hans-Rainer Trebin
Crystalsare composed of atoms in such a way that the structure repeats periodically. This is like a wall paper where you have certain decoration and this repeats to left and right up and down. In a crystal, you have this periodic pattern in three directions. So if you know what the basic pattern is, you know, what the crystal is looking at infinite distances. Now there is a certain restriction on the symmetry of periodic systems. You can rotate a square crystal for example by 90 degrees. This is called a four field rotation; because 90 degrees is 360 degrees over four. You can rotate the periodic crystal also by 60 degrees. So one has certain rotation symmetries, which means, you rotate them and they look like after the rotation and for periodic systems, this rotation is twofold, three fold, four fold, six fold and nothing else. Shechtman discovered a novel crystal, which has five fold symmetry. The question is what kind of structure is it, it cannot be periodic.
Interviewer -- Chris Smith
Indeed and obviously when he saw that, and then tried to tell people about it, everyone would have said look, we've known about crystals for 120 years, this cannot exist.
Interviewee -- Hans-Rainer Trebin
Yeah, well nobody believed that such a structure is possible in particular, since it showed certain features in electron microscopy, certain reflections, which had also five-fold symmetry. So the question is something ordered and not periodic. This one could not imagine what it'd mean?
Interviewer -- Chris Smith
What was the material he was actually looking at, when he made this discovery?
Interviewee -- Hans-Rainer Trebin
Well he was looking for light-weighted materials, which you can use in aeronautics, this was aluminium alloys. It was aluminium-manganese and later also aluminium iron
Interviewer -- Chris Smith
So once he had begun to explore how this could happen, how did he discover actually what was going on that there must be this five-fold symmetry which totally broke the mould as far as crystal architectures had been before.
Interviewee -- Hans-Rainer Trebin
Well, there was some discussion by theoreticians at this time about this five-fold symmetry. In particular there was this pattern, which British mathematician and physicist, Penrose, had proposed 10 years prior, the so called Penrose pattern. It consists of two types of rhombohedra which you have to put aside according to certain rules and which has a five-fold symmetry and which is not periodic. So this pattern, one was looking at and the proposal was that this structure of this aluminium-manganese is following the Penrose pattern.
Interviewer -- Chris Smith
So, how did they then take that forward to ask okay, we've got a mathematical theory but translating that to something which you can physically see in a chemical is a different matter, so how did they do that?
Interviewee -- Hans-Rainer Trebin
Well, that's the interesting thing that things which mathematicians have thought appear always in nature. This is a rule, a very, very nice rule. One could extend this Penrose pattern to three-dimensions. The explanation was you take, you tie it in out space, three-dimensional space, not with two types of rhombus but with two types of rhombohedra and then you get the symmetry, which also Shechtman discovered which are equals of hedral symmetry. It was like a three-dimensional Penrose pattern. Of course, he took this rhombohedra and to one head to put atoms in a certain way, at special places of this rhombohedra, this one could do and one had an approximate structure for this aluminium-manganese quasicrystal.
Interviewer -- Chris Smith
But what's the really important thing here. The fact that we've proved that this can exist, does exist, and it's borne out by both mathematical and observational models, but chemically speaking why is it important, how does it change the lives of everyone on the planet?
Interviewee -- Hans-Rainer Trebin
The structure is determining also the properties of physical subjects. Structure is as important as the elements. Yet, metallic elements but the structure then induced non-metallic properties. For example, a medal has low resistance for electric current. These quasicrystals have a high resistance. A metal can be easily bent. These quasicrystals are very hard and brittle. So you have non-metallic properties induced in a structure of metallic atoms and so you now can play around with metal and induce now properties which you can use in an industry for example or in applications.
Interviewer -- Chris Smith
Are they very easy to initiate, if you want to give a quasicrystal architecture with this five-fold symmetry to a material, which would normally not form that particular organization, can you inflict that configuration upon it?
Interviewee -- Hans-Rainer Trebin
Well, one has now investigated very closely the electronic properties of these quasicrystals and there are certain rules for which, which are valid for quasi crystals and these rules have been applied in particular by Japanese material scientists and following these rules they could synthesize, well hundreds of new substances. These rules are somewhat easy to express. You have to have a certain number of electrons, which participate in the construction of these solids. Valence electrons per atom must follow certain numbers, and once you know that, you might be able to synthesize a quasicrystal.
(29:37 - Chameleon clothes to detect falling oxygen levels)
Interviewer -- Chris Smith
Hans-Rainer Trebin from Stuttgart University. Now to a colourful line of chemical research, Laura.
Interviewee - Laura Howes
Yes this is about chameleon clothes. This is talking about using a smart material to tell you when you're in an area with low oxygen levels.
Interviewer-- Chris Smith
Aren't there plenty of pubs which have terrible lack of atmosphere, never been that deprived of oxygen though, why would this be useful?
Interviewee - Laura Howes
Well, you know, in your everyday life, you might not have that many reasons to worry about the oxygen levels but there are certain jobs where this will be a problem, for example, mining. So Xi Chen from Xiamen University in China who is the person, whose done this work was actually inspired by seeing these coal miners getting trapped underground and having problems with lack of oxygen and that's actually what inspired him to do this work.
Interviewer -- Chris Smith
How does it work?
Interviewee - Laura Howes
They basically take just a normal thread of cotton, into that they sort of inculcate these polystyrene microparticles. They're small, very small balls of polystyrene and not quite like having a beanbag, but a bit smaller than that, and then attached to that are two dyes, there is a blue dye and a red dye. The blue dye is like a reference dye that stays given the same amount of blue. The red dye is reactive to the amount of oxygen. So if there's decent amount of oxygen in the atmosphere, you're going to get purple colour. If the oxygen level dies down then the red colour dies down and then you get a change to a more blue colour.
Interviewer - Chris Smith
And so that's the visual read out.
Interviewee - Laura Howes
So, that's the visual readout, but there's actually more. So that's the sort of qualitative 'oh look, there's a problem'. Because of the dyes that have been chosen, you can actually also get a quantitative readout if you use a digital camera because the two dyes are chosen because they match up with the sensors in your digital camera. So, if you have one and you take snapshot, you can actually read the colour and get a percentage of where the oxygen level is.
Interviewer -- Chris Smith
Is it linear, in other words, do we know what colour you get in proportion to what amounts of oxygen, so you can literally read it off as a percentage?
Interviewee - Laura Howes
Yeah. You can literally sort of read off as a sort of a percentage, yeah.
Interviewer -- Chris Smith
So would you actually wear this, or would it be better to have some kind of badge or something?
Interviewee - Laura Howes
Yeah I mean possibly it would be better to have a badge, I mean, they're talking about may be sort of some sort of embroidery into your uniform, so you wouldn't be wearing a whole outfit that which changes colours as you dance around.
Interviewer -- Chris Smith
Are we far away from fabricating this? Is it done?
Interviewee - Laura Howes
I think fabrication is completely doable and people have outfits with microencapsulation already. I think more the issue is in a way there is a solution to may be a question that wasn't necessarily being asked.
(32:23 - Patching up patients with a heart of gold)
Interviewer -- Chris Smith
Yet, another ingenious and very simple solution to a problem, but again I can't believe that no one thought of it before, Thank you Laura. Now Patrick, let's get out from outside of the body to inside the body and this is an interesting story about patching up people's hearts
Interviewee -- Patrick Walter
Patching up their hearts with a heart of gold. So people who suffer heart damage, the best thing to do would be to try and replace that tissue with some undamaged tissue. Currently, people have been trying to grow up things like cardiac myocytes in scaffolds, but the problem is these myocytes don't communicate very well with each other. So what Daniel Kohane at Harvard Medical School has done is he's tried to connect them up properly. So just like an electrician who go around your house and he'll connect everything up back to one fuse box, that's what he's trying to do with these cells.
Interviewer -- Chris Smith
Oh I see, so in the heart, where we rely on a coordinated beating in the right sequence of cells, each cell in turn contracting in order to make a coordinated contraction of the heart, if you could just have random cells been put into a previously damaged bit of the heart and they're not connected up, you won't get that useful connected, synchronous behaviour and you're saying, maybe we could come up with a way of actually physically connecting the cells together in order to achieve that.
Interviewee -- Patrick Walter
Exactly. Yes. So often they use scaffolds and things like alginates which are extracted from sea weeds, so you can build up these 3D scaffolds and build up nice sort of structures of cells that are quite thick and would be good for filling in like for damaged tissue, but the problem with these alginate scaffolds is that cells won't talk to each other because they get stuck in these pores and then they can't communicate across the pore walls. So, what this group did was when they're formulating the alginate scaffolds, they dumped a whole load of gold nanorods, nanowires into the alginates. These are about a micron long and the walls of the actual scaffold are about 500 nanometers thick so lots of these nanowires would have penetrated the walls.
Interviewer -- Chris Smith
So it's like a premade wiring loom in control of all the cells.
Interviewee -- Patrick Walter
Exactly, yeah, yeah. So all the cells are basically in contact with the others through these gold nanowires.
Interviewer -- Chris Smith
Do they work?
Interviewee -- Patrick Walter
Yeah. I mean they did some tests and what they found was when you stimulate these myocytes, you get propagation of electrical signals in an organized manner across the whole patch, the start of one end and then they'll gradually move across, contracting as they go.
Interviewer -- Chris Smith
But how do you know though that it is not just a stimulus that you've put in to excite one of the cells, just going down the wires and then retreating the cells on their way? Is it actually physically the cells transmitting their own currents along the wires to each other?
Interviewee -- Patrick Walter
Okay, so all the wires aren't all linked up. They're kind of randomly dropped into the scaffold. So if you stimulate at one end, it shouldn't be just going on the wire, although you never know, but I think the researchers have already looked into that.
Interviewer -- Chris Smith
So, basically it got to be that a cell goes off, it gets excited and then the current from that cell passes down the wire to the next cell.
Interviewee -- Patrick Walter
Yeah.
Interviewer -- Chris Smith
So this is in-vitro though isn't it? So they haven't actually taken those patches with the nanowires and put them in-vivo yet.
Interviewee -- Patrick Walter
Yep, that's right. So they're still just working with cell cultures really. They're just working with the cultures in scaffolds. So the next thing is to move onto to trying to put into animals. I mean, Daniel Kohane himself says it's still a bit of a way off from actually getting into people, so he still thinks it's quite a few years away from that.
Interviewer -- Chris Smith
And just on the subject of gold, is it okay to put things like gold nano-rods, into people. Are they biocompatible?
Interviewee -- Patrick Walter
They say that it's one of the advanced things like gold nanoparticles, gold nanowires. They can be functionalized to actually make them nontoxic, so you would end up with a heart of gold but your heart would be fixed
Interviewer -- Chris Smith
Unlike Patrick's poor puns, which are nearly as bad as mine, but stay there Patrick, because it says here you want to talk about mole day.
(36:14 - Trivia - Why is 23 October an important day for chemists?)
Interviewee -- Patrick Walter
Right. So, do you know what's special about the 23rd of October?
Interviewer -- Chris Smith
No obviously Halloween is the 31st, but I guess that's not relevant. So no, I don't know, what's special about the 23rd of the 10th?
Interviewee -- Patrick Walter
Well chemists were celebrating it between 6:02 am and 6:02 pm, which might give you a clue.
Interviewer -- Chris Smith
6.02, well, it's sort of got the beginnings of Avogadro's number there?
Interviewee -- Patrick Walter
Exactly yes.
Interviewer -- Chris Smith
Is that relevant?
Interviewee -- Patrick Walter
Yes. 6.02 am times 10th month 23, October 23rd. So there you go.
Interviewer -- Chris Smith
Avogadro number, okay right.
Interviewee -- Patrick Walter
So, this obviously works bit better if you're in the US because the month comes before the date, but it is principally celebrated in the US. So it's all about trying to raise the profile of chemistry and get students interested in it.
Interviewer -- Chris Smith
Okay so what will you be doing for mole day then?
Interviewee -- Patrick Walter
I think as many cheesy jokes possible about moles could work.
Interviewer -- Chris Smith
Okay got one. What do you call a tooth in a glass of water?
Interviewee -- Patrick Walter
I don't know. What do you call a tooth in a glass of water.
Interviewer -- Chris Smith
I can barely bring it myself because I'm going to eclipse you. It's a one molar solution.
Interviewee -- Patrick Walter
Of course it is.
Interviewer -- Chris Smith
Now tell us seriously, tell us a little bit about Avogadro and why this mole day is important?
Interviewee -- Patrick Walter
Okay, so Avogadro was the guy who worked out the number of atoms you would have in 12 grams of carbon 12. So this is a way chemists can work out how much a reactant they're using in a chemical reaction. So, for instance, water, has an atomic mass of 18, so 16 for oxygen and 2 for the two hydrogens. So if you had 18 grams of water, you would know that's one mole. So it's a way to simply know how much you've got of the substance. The whole idea of mole day, it came out back in the '80s, but didn't really gain any traction till a bit later on perhaps the '90s when school teachers across the US started trying to promote mole day as a way to raise the profile for chemistry, get kids interested and also to just let people know all about Avogadro and the idea behind moles, I mean it's also GCSE chemistry.
Interviewer -- Chris Smith
And that's where we must leave it for this month. Thank you to Phil Broadwith, Laura Howes and Patrick Walter and our guest, John Grotzinger and Hans-Rainer Trebin. Production this month was by Meera Senthilingam and I'm Chris Smith from thenakedscientists dot com. There's more cutting edge chemistry next month. But until then, good bye.
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The Chemistry World Podcast is brought to you by the Royal Society of Chemistry. Look us up online at chemistryworld dot org.
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